diff --git a/packages/server/src/ws.modifier-profile-consent.test.ts b/packages/server/src/ws.modifier-profile-consent.test.ts
new file mode 100644
index 0000000..41a8d7b
--- /dev/null
+++ b/packages/server/src/ws.modifier-profile-consent.test.ts
@@ -0,0 +1,475 @@
+/**
+ * T3 integration tests: two-player consent flow
+ * (`modifier-profile.propose` / `modifier-profile.consent`) per
+ * T2-ADR-2.
+ *
+ * Covers:
+ *   1. Host proposes -> opponent receives `proposal-pending`;
+ *      proposer receives `modifier-profile.queued` ack only.
+ *   2. Opponent approves -> proposer gets `consent-received`,
+ *      profile promoted to Room.pendingProfile (T2 queue).
+ *   3. Opponent rejects -> both get
+ *      `modifier-profile.rejected` reason `"rejected"`.
+ *   4. Timeout (vi.useFakeTimers) -> both get `rejected` reason
+ *      `"timeout"`.
+ *   5. Self-consent -> proposer's `consent` attempt returns
+ *      `INVALID_MESSAGE`; proposal remains active.
+ *   6. Supersession -> a second `propose` broadcasts
+ *      `rejected` reason `"superseded"` for the first BEFORE
+ *      sending `proposal-pending` for the second.
+ *   7. Solo mode (1 player) rejects `propose` with guidance.
+ *
+ * Harness mirrors `ws.modifier-profile-update.test.ts`.
+ */
+import type { ServerWebSocket } from "bun";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import {
+  handleMessage,
+  registerConnection,
+  roomRegistry,
+  sessionRegistry,
+  type ClientData,
+} from "./broadcast.js";
+import { PROTOCOL_VERSION, type ClientMessage } from "./protocol.js";
+
+// --- Mock ServerWebSocket harness ------------------------------------
+
+interface MockWs extends ServerWebSocket<ClientData> {
+  readonly sent: unknown[];
+  readonly closed: boolean;
+}
+
+function makeMockWs(clientId: string): MockWs {
+  const sent: unknown[] = [];
+  const closedFlag = { value: false };
+  const ws = {
+    data: { clientId } as ClientData,
+    sent,
+    get closed(): boolean {
+      return closedFlag.value;
+    },
+    send(msg: string | Buffer): number {
+      const str = typeof msg === "string" ? msg : msg.toString("utf8");
+      sent.push(JSON.parse(str));
+      return str.length;
+    },
+    close(): void {
+      closedFlag.value = true;
+    },
+  } as unknown as MockWs;
+  return ws;
+}
+
+function nextMsgOfType(
+  ws: MockWs,
+  type: string,
+): { payload: Record<string, unknown> } {
+  const idx = ws.sent.findIndex(
+    (m) =>
+      typeof m === "object" &&
+      m !== null &&
+      (m as { type: unknown }).type === type,
+  );
+  if (idx < 0) {
+    const types = ws.sent.map((m) => (m as { type?: string }).type);
+    throw new Error(
+      `no message of type "${type}" in inbox (got ${JSON.stringify(types)})`,
+    );
+  }
+  const msg = ws.sent[idx] as { payload: Record<string, unknown> };
+  ws.sent.splice(idx, 1);
+  return msg;
+}
+
+function hasMsgOfType(ws: MockWs, type: string): boolean {
+  return ws.sent.some(
+    (m) =>
+      typeof m === "object" &&
+      m !== null &&
+      (m as { type?: string }).type === type,
+  );
+}
+
+function sendClient(
+  ws: MockWs,
+  type: ClientMessage["type"],
+  payload: unknown,
+  seq = 1,
+): void {
+  handleMessage(
+    ws,
+    JSON.stringify({
+      v: PROTOCOL_VERSION,
+      seq,
+      ts: Date.now(),
+      type,
+      payload,
+    }),
+  );
+}
+
+// --- Profile fixtures ------------------------------------------------
+
+const initialProfile = {
+  id: "t3-initial",
+  name: "Initial",
+  description: "White pawns +1 HP.",
+  layoutId: "classic",
+  perType: [
+    {
+      kind: "hp-bonus" as const,
+      pieceType: "pawn" as const,
+      color: "white" as const,
+      value: 1,
+    },
+  ],
+  perInstance: [],
+  version: 1 as const,
+  source: "custom" as const,
+};
+
+const candidateA = {
+  id: "t3-candidate-a",
+  name: "Candidate A",
+  description: "Rooks +1 range.",
+  layoutId: "classic",
+  perType: [
+    {
+      kind: "range-bonus" as const,
+      pieceType: "rook" as const,
+      color: "both" as const,
+      value: 1,
+    },
+  ],
+  perInstance: [],
+  version: 1 as const,
+  source: "custom" as const,
+};
+
+const candidateB = {
+  id: "t3-candidate-b",
+  name: "Candidate B",
+  description: "Bishops +1 range.",
+  layoutId: "classic",
+  perType: [
+    {
+      kind: "range-bonus" as const,
+      pieceType: "bishop" as const,
+      color: "both" as const,
+      value: 1,
+    },
+  ],
+  perInstance: [],
+  version: 1 as const,
+  source: "custom" as const,
+};
+
+function proposePayload(
+  roomCode: string,
+  candidate: Record<string, unknown>,
+  version: number,
+): Record<string, unknown> {
+  return { roomCode, candidate, version };
+}
+
+function consentPayload(
+  roomCode: string,
+  decision: "approve" | "reject",
+): Record<string, unknown> {
+  return { roomCode, decision };
+}
+
+// --- Setup helpers ---------------------------------------------------
+
+/** Multiplayer room (2 filled slots) with an initial profile at v1. */
+function setupMultiplayerRoom(): {
+  white: MockWs;
+  black: MockWs;
+  code: string;
+} {
+  const white = makeMockWs(`T3-W-${crypto.randomUUID()}`);
+  const black = makeMockWs(`T3-B-${crypto.randomUUID()}`);
+  registerConnection(white);
+  registerConnection(black);
+
+  sendClient(white, "room.create", { profile: initialProfile });
+  const created = nextMsgOfType(white, "room.created");
+  const code = created.payload["code"] as string;
+
+  sendClient(black, "room.join", { code });
+  nextMsgOfType(black, "room.joined");
+  if (hasMsgOfType(white, "game.state")) nextMsgOfType(white, "game.state");
+  if (hasMsgOfType(black, "game.state")) nextMsgOfType(black, "game.state");
+
+  return { white, black, code };
+}
+
+/** Solo room (1 filled slot). */
+function setupSoloRoom(): { white: MockWs; code: string } {
+  const white = makeMockWs(`T3-SOLO-${crypto.randomUUID()}`);
+  registerConnection(white);
+  sendClient(white, "room.create", { profile: initialProfile });
+  const created = nextMsgOfType(white, "room.created");
+  const code = created.payload["code"] as string;
+  return { white, code };
+}
+
+// --- Tests -----------------------------------------------------------
+
+describe("modifier-profile.propose/consent (T3)", () => {
+  afterEach(() => {
+    // Clear any dangling proposalState that would leak into the
+    // next test's room via the module-scoped registry. Each test
+    // creates a fresh room code so registry leakage is cosmetic
+    // rather than functional, but cleaning up keeps timer-based
+    // tests deterministic.
+    vi.useRealTimers();
+  });
+
+  it("propose -> opponent gets proposal-pending; proposer gets queued ack only", () => {
+    const { white, black, code } = setupMultiplayerRoom();
+
+    sendClient(
+      white,
+      "modifier-profile.propose",
+      proposePayload(code, candidateA, 1),
+    );
+
+    // Proposer ack (T2 queued shape reused).
+    const ack = nextMsgOfType(white, "modifier-profile.queued");
+    expect(ack.payload["roomCode"]).toBe(code);
+    expect(ack.payload["pendingVersion"]).toBe(2);
+
+    // Proposer does NOT get their own proposal-pending.
+    expect(hasMsgOfType(white, "modifier-profile.proposal-pending")).toBe(
+      false,
+    );
+
+    // Opponent receives proposal-pending.
+    const pending = nextMsgOfType(black, "modifier-profile.proposal-pending");
+    expect(pending.payload["roomCode"]).toBe(code);
+    expect(pending.payload["proposer"]).toBe("white");
+    expect((pending.payload["profile"] as { id: string }).id).toBe(
+      candidateA.id,
+    );
+    expect(typeof pending.payload["expiresAt"]).toBe("number");
+
+    // Room has proposalState.
+    const room = roomRegistry.getRoom(code)!;
+    expect(room.proposalState?.profile.id).toBe(candidateA.id);
+    expect(room.proposalState?.proposedBy).toBe("white");
+
+    // No pendingProfile yet (only installed on approve).
+    expect(room.pendingProfile).toBeUndefined();
+  });
+
+  it("approve -> proposer gets consent-received; profile enters T2 pending queue", () => {
+    const { white, black, code } = setupMultiplayerRoom();
+
+    sendClient(
+      white,
+      "modifier-profile.propose",
+      proposePayload(code, candidateA, 1),
+    );
+    nextMsgOfType(white, "modifier-profile.queued");
+    nextMsgOfType(black, "modifier-profile.proposal-pending");
+
+    sendClient(
+      black,
+      "modifier-profile.consent",
+      consentPayload(code, "approve"),
+    );
+
+    // Proposer receives consent-received.
+    const approved = nextMsgOfType(white, "modifier-profile.consent-received");
+    expect(approved.payload["roomCode"]).toBe(code);
+
+    // Opponent (who approved) doesn't hear a consent-received —
+    // they already know they approved.
+    expect(hasMsgOfType(black, "modifier-profile.consent-received")).toBe(
+      false,
+    );
+
+    // No rejected broadcast on approve.
+    expect(hasMsgOfType(white, "modifier-profile.rejected")).toBe(false);
+    expect(hasMsgOfType(black, "modifier-profile.rejected")).toBe(false);
+
+    // proposalState drained, pending slot populated with the
+    // proposer's token for apply-time NACK routing.
+    const room = roomRegistry.getRoom(code)!;
+    expect(room.proposalState).toBeUndefined();
+    expect(room.pendingProfile?.id).toBe(candidateA.id);
+    // Version hasn't bumped yet (only on apply at turn boundary).
+    expect(sessionRegistry.get(code)?.getProfileVersion()).toBe(1);
+
+    // Next move drains the queue and broadcasts updated to both.
+    sendClient(white, "game.move", { from: "e2", to: "e4" });
+    const wUpd = nextMsgOfType(white, "modifier-profile.updated");
+    const bUpd = nextMsgOfType(black, "modifier-profile.updated");
+    expect(wUpd.payload["version"]).toBe(2);
+    expect(bUpd.payload["version"]).toBe(2);
+    expect((wUpd.payload["profile"] as { id: string }).id).toBe(candidateA.id);
+  });
+
+  it("reject -> both get modifier-profile.rejected reason=rejected; no queue entry", () => {
+    const { white, black, code } = setupMultiplayerRoom();
+
+    sendClient(
+      white,
+      "modifier-profile.propose",
+      proposePayload(code, candidateA, 1),
+    );
+    nextMsgOfType(white, "modifier-profile.queued");
+    nextMsgOfType(black, "modifier-profile.proposal-pending");
+
+    sendClient(
+      black,
+      "modifier-profile.consent",
+      consentPayload(code, "reject"),
+    );
+
+    const wRej = nextMsgOfType(white, "modifier-profile.rejected");
+    const bRej = nextMsgOfType(black, "modifier-profile.rejected");
+    expect(wRej.payload["reason"]).toBe("rejected");
+    expect(bRej.payload["reason"]).toBe("rejected");
+
+    // No consent-received on reject.
+    expect(hasMsgOfType(white, "modifier-profile.consent-received")).toBe(
+      false,
+    );
+
+    const room = roomRegistry.getRoom(code)!;
+    expect(room.proposalState).toBeUndefined();
+    expect(room.pendingProfile).toBeUndefined();
+  });
+
+  it("60s timeout -> both get modifier-profile.rejected reason=timeout", () => {
+    vi.useFakeTimers();
+    const { white, black, code } = setupMultiplayerRoom();
+
+    sendClient(
+      white,
+      "modifier-profile.propose",
+      proposePayload(code, candidateA, 1),
+    );
+    nextMsgOfType(white, "modifier-profile.queued");
+    nextMsgOfType(black, "modifier-profile.proposal-pending");
+
+    // Before the timeout nothing fires.
+    vi.advanceTimersByTime(59_999);
+    expect(hasMsgOfType(white, "modifier-profile.rejected")).toBe(false);
+    expect(hasMsgOfType(black, "modifier-profile.rejected")).toBe(false);
+
+    // Cross the 60s boundary.
+    vi.advanceTimersByTime(2);
+
+    const wRej = nextMsgOfType(white, "modifier-profile.rejected");
+    const bRej = nextMsgOfType(black, "modifier-profile.rejected");
+    expect(wRej.payload["reason"]).toBe("timeout");
+    expect(bRej.payload["reason"]).toBe("timeout");
+
+    const room = roomRegistry.getRoom(code)!;
+    expect(room.proposalState).toBeUndefined();
+    expect(room.pendingProfile).toBeUndefined();
+  });
+
+  it("self-consent -> proposer rejected with INVALID_MESSAGE; proposal unchanged", () => {
+    const { white, black, code } = setupMultiplayerRoom();
+
+    sendClient(
+      white,
+      "modifier-profile.propose",
+      proposePayload(code, candidateA, 1),
+    );
+    nextMsgOfType(white, "modifier-profile.queued");
+    nextMsgOfType(black, "modifier-profile.proposal-pending");
+
+    // Proposer tries to approve their own proposal.
+    sendClient(
+      white,
+      "modifier-profile.consent",
+      consentPayload(code, "approve"),
+    );
+
+    const err = nextMsgOfType(white, "error");
+    expect(err.payload["code"]).toBe("INVALID_MESSAGE");
+    expect(String(err.payload["message"])).toMatch(/self-consent/i);
+
+    // Proposal still active; no broadcasts fired.
+    const room = roomRegistry.getRoom(code)!;
+    expect(room.proposalState?.profile.id).toBe(candidateA.id);
+    expect(hasMsgOfType(white, "modifier-profile.consent-received")).toBe(
+      false,
+    );
+    expect(hasMsgOfType(white, "modifier-profile.rejected")).toBe(false);
+    expect(hasMsgOfType(black, "modifier-profile.rejected")).toBe(false);
+  });
+
+  it("supersession -> second propose broadcasts rejected(superseded) for first, THEN sends new proposal-pending", () => {
+    const { white, black, code } = setupMultiplayerRoom();
+
+    // First propose (candidateA).
+    sendClient(
+      white,
+      "modifier-profile.propose",
+      proposePayload(code, candidateA, 1),
+    );
+    nextMsgOfType(white, "modifier-profile.queued");
+    nextMsgOfType(black, "modifier-profile.proposal-pending");
+
+    // Drain the proposer-ack from the second so we can inspect
+    // the wire ordering on both sockets cleanly.
+    sendClient(
+      white,
+      "modifier-profile.propose",
+      proposePayload(code, candidateB, 1),
+    );
+
+    // White should now have: rejected(superseded) followed by
+    // queued ack for the NEW proposal. Order matters: the spec
+    // requires superseded to arrive before the new proposal's
+    // receipt confirmation.
+    const wRej = nextMsgOfType(white, "modifier-profile.rejected");
+    expect(wRej.payload["reason"]).toBe("superseded");
+    const wQueued = nextMsgOfType(white, "modifier-profile.queued");
+    expect(wQueued.payload["pendingVersion"]).toBe(2);
+
+    // Black also sees rejected(superseded) first, then the new
+    // proposal-pending.
+    const bRej = nextMsgOfType(black, "modifier-profile.rejected");
+    expect(bRej.payload["reason"]).toBe("superseded");
+    const bNewPending = nextMsgOfType(
+      black,
+      "modifier-profile.proposal-pending",
+    );
+    expect((bNewPending.payload["profile"] as { id: string }).id).toBe(
+      candidateB.id,
+    );
+
+    // Room now has the second proposal only.
+    const room = roomRegistry.getRoom(code)!;
+    expect(room.proposalState?.profile.id).toBe(candidateB.id);
+  });
+
+  it("solo mode -> propose rejected with guidance to use modifier-profile.update", () => {
+    const { white, code } = setupSoloRoom();
+
+    sendClient(
+      white,
+      "modifier-profile.propose",
+      proposePayload(code, candidateA, 1),
+    );
+
+    const err = nextMsgOfType(white, "error");
+    expect(err.payload["code"]).toBe("INVALID_MESSAGE");
+    expect(String(err.payload["message"])).toMatch(
+      /2 players|modifier-profile\.update/i,
+    );
+
+    // No proposalState installed, no queued ack fired.
+    const room = roomRegistry.getRoom(code)!;
+    expect(room.proposalState).toBeUndefined();
+    expect(hasMsgOfType(white, "modifier-profile.queued")).toBe(false);
+  });
+});